1. Field of the Invention
This invention relates to the field of photography, and more specifically to a combined shutter and adjustable aperture in a photographic camera including a plurality of blades and a stepper motor for moving the blades between a closed position and multiple open or exposure positions.
2. Description of the Prior Art
It is known in the prior art to provide apparatus that combines the photographic functions of an adjustable exposure aperture and a shutter. Typically two rectangular blades, each including a tear-shaped hole therein, are mounted for relative reciprocating movement between a closed position and a plurality of open positions. In the closed position the holes are offset and the blades act as a shutter to block exposures. In the open positions the holes overlap by increasing amounts to define multiple exposure apertures that increase in size with the amount of overlap of the holes in the blades. Frequently the blades are driven between their respective positions by a stepper motor under the influence of a control circuit. The control circuit includes sensors which determine the exposure conditions of the subject. It then actuates the motor to drive the blades open to the appropriate aperture. The control also determines a suitable time interval for the exposure at that aperture and energizes the motor to close the blades.